Twenty-three nations, about 40 ships, six submarines, hundreds of aircraft and 25,000 people are participating in this year’s Rim of the Pacific war games in and around Hawaii June 26 to Aug. 1, the Navy said.

Details until now have been few, but Navy officials released some of the specifics of this summer’s iteration of the world’s largest international maritime exercise.

Those include China’s participation for the first time as some raise concerns that forays by the rising Asian power into blue waters far from its country are largely about countering the U.S. Pacific Fleet.

The People’s Liberation Army-Navy is scheduled to send four ships to RIMPAC, the Navy said.

The hospital ship Peace Ark will take part in medical exchanges and exercises, and an oiler, frigate and destroyer will participate in a "maritime interdiction operations" task force under a U.S. Coast Guard cutter commanding officer, Lt. Lenaya Rot­klein, a spokes­woman for the Navy’s 3rd Fleet in San Diego, said Monday.

Th 3rd Fleet helps plan RIMPAC.

A U.S. Navy ship and Chinese ships Harbin, a destroyer, and oiler Wei­shanhu conducted maritime interdiction operations, including a counterpiracy exercise, in the Gulf of Aden in August.

The Pentagon said the exercise was "a big step beyond" the first counterpiracy exercise between the U.S. and Chinese navies in 2012.

A small Chinese contingent did observe RIMPAC in 1998, the Navy previously said. But the National Defense Authorization Act of 2000 prohibits military-to-military contact with the People’s Liberation Army if that contact would "create a national security risk" due to exposure to operational areas including advanced combined-arms and joint combat operations.

Adm. Harry B. Harris Jr., head of U.S. Pacific Fleet, said earlier this month in Australia in prepared remarks that he is "concerned by the aggressive growth of the Chinese military."

But he also said China’s participation in RIMPAC will be an important milestone.

"Despite the concerns I’ve mentioned, we welcome the emergence of a peaceful, responsible and prosperous China as a positive contributor to Asian stability," Harris said.

This year’s exercise includes units or personnel from Australia, Brunei, Canada, Chile, Colombia, France, India, Indonesia, Japan, Malaysia, Mexico, the Netherlands, New Zealand, Norway, People’s Republic of China, Peru, the Republic of Korea, the Republic of the Philippines, Singapore, Thailand, Tonga, the United Kingdom and the United States.

The aircraft carrier USS Ronald Rea­gan and amphibious assault ship USS Pele­liu will be among the biggest ships to take part in the upcoming RIMPAC, which is held every other year off Hawaii.

Four ships are scheduled to participate in a portion of the exercise off Southern Cali­for­nia.

The exercise will be divided into a "harbor phase" to build relationships and reinforce protocols; scripted exercises with gunnery, ship sinkings, an amphibious rehearsal and humanitarian assistance and disaster relief; and large-scale, multilateral, unscripted exercises.

Two sinking exercises, or "SINKEXs," are planned with the ex-Ogden confirmed and either the ex-Racine or ex-Tuscaloosa to be the other old ship to be deep-sixed, 3rd Fleet’s Rotklein said.

Six submarines are scheduled for the war games, highlighting the importance of submarine warfare.

December planning slides for RIMPAC indicated that the lineup included the U.S. subs Houston, City of Corpus Christi and Santa Fe; Australia sub HMAS Waller; Canadian sub HMCS Victoria; and a South Korean submarine.

A fire occurred on the Waller in February. The Navy said six submarines still are expected, but the list has changed since the December planning session.

The maritime interdiction operation involving the Chinese destroyer, frigate and oiler was referenced in December by the Navy as being under the Coast Guard cutter Waesche and including two Royal Brunei Navy ships, a French frigate, a U.S. frigate and the Pearl Harbor-based cruiser USS Port Royal.

As part of a conflict simulation, the Hawaiian Islands were divided into four fictional "Coaster Islands" countries: Griffon, Orion, Yolo and Pandora, according to the December RIMPAC planning slides, which were posted on the Internet in February.

Oahu and Kauai are part of Griffon, while Maui, Lanai and Molo­kai are Yolo. Hawaii island is Orion, and Pandora is delineated by a sea area to the west of Kauai.

Griffon, a liberal demo­cratic republic, is the economic driver in the region and has strong ties to the RIMPAC nations.

Orion is a military dictatorship that was the result of a military coup that took place in the early 1990s. Orion has the strongest military within the Coaster Islands and is led by an expansionist regime.

Piracy within the region is on the rise, as are hostilities by Orion toward Griffon. Orion harassment of Griffon shipping includes detaining merchant vessels, siphoning of refined oil products and eventually firing upon and sinking vessels.

The "armed resistance movement" is a terrorist organization that increases its influence within Griffon with the main aim of creating instability to undermine the government.

The "mission statement" for that portion of the exercise is to deploy forces to the Coaster Islands in order to restore freedom of navigation, expel the armed resistance movement from Griffon and Yolo, and deter aggression within the islands.

The 3rd Fleet’s Rotklein said some aspects of the scenario have changed since December but that those changes wouldn’t be discussed "in order to preserve a degree of realism for the participants."

"U.S. 3rd Fleet has worked with political advisers from participating nations to add realistic and relevant details to the scenario, to include United Nations Security Council resolutions," but the scenario has no relationship to any particular area of the world, Rotklein said.